|When you see lightning.|
Being struck by lightning is usually fatal. So, anytime lightning is nearby you should seek shelter inside a building or a car. Both are constructed to direct the lightning's power safely away from you, should a strike occur.
Lightning is unpredictable, but will usually strike the tallest object in the area. If you are standing in an open field you may well be the tallest object. Golfers are often lightning strike victims because they are likely to be out in the open when a lightning storm begins.
Standing by the only tall tree in an area isn't really a good idea. If lightning strikes the tree the ground near the tree may carry the charge to you. If you can't get indoors, stay low and keep away from high places and metal objects, which seem to attract lightning strikes.
If your are swimming when a lightning storm begins, come out of the water. Water is an excellent conductor of electricity. A lightning strike could hurt you even if it strikes the water far from you.
Again, the best thing to do during a lightning storm is to go indoors, or wait in a car, until the storm passes.
How Close is the Lightning?
How can you tell how far you are from the lightning, and whether it's moving closer?
When you see a lightning, count the seconds until you hear the thunder.
Now, multiply the seconds by five. The product equals the number of miles to the lightning.